brake lights

[4129R]

Check for power on the Green/Purple wire on terminal 5 on that relay, when the brakes are pushed. That is the trigger in.

This in turn should trigger the relay to give power to both Green and Red, and Green and White wires, terminals 3 and 7 on that relay. 

[4380r]

I'll give it a try.

Although where the relay is located I can't tell which terminal is which. And will have to put some thought into how the brake will be depressed while I'm laying under there with my mulimeter. 

[4129R]

You should be almost on top of the brake pedal when you are upside down under the steering column looking up at the relay.

Beware, it is not and easy position to get out of, and removing the steering wheel makes it a whole lot easier.

[4380r]

If I am laying on my back under the dash, head against the firewall, looking up at the relay (the ends of which peak out from behind the steering wheel bracket, the middle terminals look very hard to access with relay in place), what is the orientation of the terminals?

Wiring diagram indicates 1 and 5 are on the extreme left, 4 and 8 the extreme right.

Laying there I'm looking up at the relay and see the metal housing. Is that the same 'view' as on the wiring diagram, or is the diagram looking at the relay from the other side?

Thanks

[4129R]

You will have to trace them through the colours:-

1 is green/brown     5 is green/purple
2 is green/white      6 is green/red
3 is green/white      7 is green/red
4 is green/white      8 is green/red

You need to find if 3 and 7 are active as those go to the red RH and rear LH brake light, respectively.

[4380r]

You will have to trace them through the colours:-

1 is green/brown     5 is green/purple
2 is green/white      6 is green/red
3 is green/white      7 is green/red
4 is green/white      8 is green/red

You need to find if 3 and 7 are active as those go to the red RH and rear LH brake light, respectively.

I do see that in the wiring diagram bug, ahh, there is the conundrum, I am partially color blind, so I was hoping to match the orientation of the terminals on the actual relay with those in the diagram.

And since I know that power is leaving the switch, I'd probably test 3 and 7 first. If the juice is going through the relay, but nothing lights, and the bulbs are ok (as evidenced by functioning of turn signals) then I know that there is a break in each of the lines heading back to each tail light, as they are independent of each other. I think it's a long shot that the only two wires a mouse chewed through would be those two lines.

[4129R]

Does this help?

[4380r]

Does this help?

That's the ticket, thanks! You could be doing something else with your evening, thanks for your help!

Come to think of it, I could be doing something more constructive at work.

[LotusJoe]

[4380r]

Thanks, Joe. I've been studying that very diagram from the KB.

[4380r]

Must be above my pay grade.

Issue: Hazards and brake lights do not work.
Tail lights and turn signals work. Conclusion #1: both filaments in both bulbs work.
Visual inspection of fuse looks good. Reverse lights work off same fuse and they are fine.
Confirmed power to and through the switch when pedal depressed.
Confirmed power gets to #5 on the relay.
Replaced original 40 year old relay with brand new one. Double checked all connections and connectors.
Power for taillights and turn signals are getting to the back of the car.
The hazard and brake lights worked until recently.
Only things hazard and brake lights have in common seem to be bulbs and relay. Both check out.

So, power gets to/through switch, to relay, bulbs work, replaced relay.

New relay no good?
Acknowledge DCO (Dreaded Current Owner) might not have installed new relay correctly. But I don't think so. It is pretty straightforward.

Hazards and brakes still don't work.

What am I missing?

[4129R]

Is there any power at 3 & 7 terminals on the relay when the brake switch is activated/shorted out?

[4380r]

Is there any power at 3 & 7 terminals on the relay when the brake switch is activated/shorted out?

I do need to check my assumption that the brand new relay would be functioning. If power is going into the relay, and it is, but not coming out where it should, then the new relay would be at fault. Maybe there is a short in the wiring that is shorting out the contacts in the relay...on the OEM and the new.

[4129R]

Until you sort out what is happening to all the wires going in and out of those 8 connections, I don't think you will trace the problem.

[Roger]

I have had some experience with this area, even making my own DB10 Relay substitute, described in Lotus Europa Central.

The brake, hazard and indicator functions share common wiring from the relay to the bulb, so if the indicators are working there's little point in trying to trace a problem there.

Try this -  test the brake lights with the Hazard Switch in both the On and Off positions. I think that if the switch is On, but you have a faulty hazard flasher unit, you will get the symptoms you describe. Worth a shot, anyway.